A clinical trial is a study aimed at answering specific questions about vaccines, new therapies or novel uses of existing treatments. Clinical trials (also called medical research and research studies) are used to determine whether new drugs or treatments are both safe and effective. There are also other clinical studies, for example, psychological and nutritional studies or experiments with medical equipment, for which healthy volunteers and patients (volunteers) are required.
Clinical Trials, with the help of volunteers, are conducted in four phases:
Phase I: Research with healthy volunteers
Phase I research is usually performed with healthy volunteers and is designed to examine the effects of a medicine in humans in order to determine its safety. Prior to a Phase I study, testing of the medicine’s safety in animals must have already been performed with acceptable results. Most phase I research begins with a single healthy volunteer who receives the lowest possible dose. If this has proven safe, more healthy volunteers are included and the dose is increased. In this phase, both the safety of the new medicine, as well as how it is processed in the body is studied. The effects of each dose are studied separately, starting with the lowest possible dose.
After the initial phase I testing, sustained treatment over the course of several consecutive days is also tested. The safety of the new medicine is closely monitored by regularly testing blood pressure and heart function, and assessing blood and urine samples. These types of testing are generally conducted in specialised phase I clinics or teaching hospitals, with expertly trained personnel and according to protocols that are designed to prevent any errors.
Phase II: Research with patients (small group)
Phase II studies are designed to determine the medication’s efficacy in the target population, i.e. patients diagnosed with the specific disease the medication is designed to treat. The safety of the medication is closely monitored throughout this phase. Blood pressure, heart function, blood and urine samples are evaluated on a regular basis, throughout the study. The efficacy of treating the patients is also studied during this phase. Testing is done to determine the optimum dose, i.e. the dose providing the greatest benefit with the least burden of side effects.
Phase III: Treatment of patients (large group)
Phase III includes much larger numbers of patients. The studies are designed to compare the new treatment to the best treatment available at the time of the study. If there is no other treatment available, the new treatment will be compared to a placebo. As larger groups are included in these studies, it is also possible to evaluate side effects that are relatively rare, and occur with a frequency of 1% or less. The results of phase III research complete the entire dossier that is submitted to the regulatory authorities for marketing approval.
Phase IV: Research with medication already on the market
Phase IV research studies treatments which are already approved and are available to patients. These studies are designed to improve the understanding of the existing medication or to treat other indications, not accounted for in previous research. As the medications studied in these trials usually have already been on the market for a while, much is already known about them. Viagra, which was initially tested and approved as a treatment for high blood pressure, is a good example. Better erections were a frequently reported side effect. The pharmaceutical company therefore researched this ‘side effect’ in a phase IV trial.